I have a public survey which some folks have been using. From android devices, they are able to submit data just fine and it all works smoothly. I have received reports from them saying that when submitting with an iphone, they are asked to sign in. I own an iPhone 6+ and tested this myself and it did ask me to sign in. This is a big issue for us as folks are not able to submit their data. Is this a bug? Timeline of it being fixed?